1. Field of the Invention
The present invention relates to a permanent magnet motor with a rotor, particularly suitable for the drive of a hand-held electric power tool and, more specifically, to a rotor of the permanent magnet motor.
2. Description of the Prior Art
The rotors of permanent magnet motors of this type have a plurality of circumferentially distributed permanent magnets which are driven in the rotating magnetic field of a stator when used appropriately in brushless permanent magnet motors. The permanent magnets are fixed in a known manner on their base body, which is preferably formed as a stack of lamellas, which sometimes is referred to as “yoke,” by gluing, plastic injection molding or by mechanical means.
According to German Publication DE 103 49 442, the permanent magnets having a certain tolerance and which are provided beforehand with baked lacquer coatings are glued to the yoke by re-melting in order to avoid plastic injection molding, which is difficult to control.
Fan blades, which are formed at an end side of an injection-molded rotor, are known from German Publication DE 44 30 073.
According to U.S. Pat. No. 6,047,460, a rotor of this type has four axially extending permanent magnets which are circumferentially distributed in a symmetrical manner and which are inserted into receptacles of an assembled yoke having axially stacked and (with the exception of the axial end caps) identically oriented sheet lamellas with a coaxial inner hole and, respectively, four closed recesses. As only two diametrically opposite recesses are mirror symmetrical with respect to one another, the sheet lamellas are rotationally symmetrical by pairs (rotated by 180°) but not by fours (rotated by 90°). Since the receptacle shape, as such, is the same in circumferentially adjacent receptacles but is not oriented in a radially mirror-reflected manner, associated homogeneously formed permanent magnets can only be used with circumferentially alternating magnet orientations, which is necessary for the rotating operation of the permanent magnet motor. Since the permanent magnets are shrinkage-fitted in a positive engagement into the yoke, which is heated beforehand, mass tolerances of the permanent magnets are not permissible in practice.